[clang] CodeGen: Make getOrEmitProtocol public for Swift

Summary:
Swift would like to use clang's apis to emit protocol declarations.

This commits adds the public API:

```
 emitObjCProtocolObject(CodeGenModule &CGM, const ObjCProtocolDecl *p);
```

rdar://60888524

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77077
diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index db78309..35b9268 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -617,6 +617,13 @@
   llvm::Value *GenerateProtocolRef(CodeGenFunction &CGF,
                                    const ObjCProtocolDecl *PD) override;
   void GenerateProtocol(const ObjCProtocolDecl *PD) override;
+
+  virtual llvm::Constant *GenerateProtocolRef(const ObjCProtocolDecl *PD);
+
+  llvm::Constant *GetOrEmitProtocol(const ObjCProtocolDecl *PD) override {
+    return GenerateProtocolRef(PD);
+  }
+
   llvm::Function *ModuleInitFunction() override;
   llvm::FunctionCallee GetPropertyGetFunction() override;
   llvm::FunctionCallee GetPropertySetFunction() override;
@@ -1348,7 +1355,7 @@
   void GenerateProtocol(const ObjCProtocolDecl *PD) override {
     // Do nothing - we only emit referenced protocols.
   }
-  llvm::Constant *GenerateProtocolRef(const ObjCProtocolDecl *PD) {
+  llvm::Constant *GenerateProtocolRef(const ObjCProtocolDecl *PD) override {
     std::string ProtocolName = PD->getNameAsString();
     auto *&Protocol = ExistingProtocols[ProtocolName];
     if (Protocol)
@@ -3039,13 +3046,18 @@
 
 llvm::Value *CGObjCGNU::GenerateProtocolRef(CodeGenFunction &CGF,
                                             const ObjCProtocolDecl *PD) {
+  auto protocol = GenerateProtocolRef(PD);
+  llvm::Type *T =
+      CGM.getTypes().ConvertType(CGM.getContext().getObjCProtoType());
+  return CGF.Builder.CreateBitCast(protocol, llvm::PointerType::getUnqual(T));
+}
+
+llvm::Constant *CGObjCGNU::GenerateProtocolRef(const ObjCProtocolDecl *PD) {
   llvm::Constant *&protocol = ExistingProtocols[PD->getNameAsString()];
   if (!protocol)
     GenerateProtocol(PD);
   assert(protocol && "Unknown protocol");
-  llvm::Type *T =
-    CGM.getTypes().ConvertType(CGM.getContext().getObjCProtoType());
-  return CGF.Builder.CreateBitCast(protocol, llvm::PointerType::getUnqual(T));
+  return protocol;
 }
 
 llvm::Constant *
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 87fd51b..3986310 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -1107,11 +1107,6 @@
 
   void GenerateProtocol(const ObjCProtocolDecl *PD) override;
 
-  /// GetOrEmitProtocol - Get the protocol object for the given
-  /// declaration, emitting it if necessary. The return value has type
-  /// ProtocolPtrTy.
-  virtual llvm::Constant *GetOrEmitProtocol(const ObjCProtocolDecl *PD)=0;
-
   /// GetOrEmitProtocolRef - Get a forward reference to the protocol
   /// object for the given declaration, emitting it if needed. These
   /// forward references will be filled in with empty bodies if no
diff --git a/clang/lib/CodeGen/CGObjCRuntime.cpp b/clang/lib/CodeGen/CGObjCRuntime.cpp
index c34758c..39efe04 100644
--- a/clang/lib/CodeGen/CGObjCRuntime.cpp
+++ b/clang/lib/CodeGen/CGObjCRuntime.cpp
@@ -13,14 +13,15 @@
 //===----------------------------------------------------------------------===//
 
 #include "CGObjCRuntime.h"
-#include "CGCleanup.h"
 #include "CGCXXABI.h"
+#include "CGCleanup.h"
 #include "CGRecordLayout.h"
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/StmtObjC.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
+#include "clang/CodeGen/CodeGenABITypes.h"
 #include "llvm/Support/SaveAndRestore.h"
 
 using namespace clang;
@@ -383,3 +384,9 @@
     CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
   return MessageSendInfo(argsInfo, signatureType);
 }
+
+llvm::Constant *
+clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
+                                       const ObjCProtocolDecl *protocol) {
+  return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);
+}
diff --git a/clang/lib/CodeGen/CGObjCRuntime.h b/clang/lib/CodeGen/CGObjCRuntime.h
index f0b3525..a2c1895 100644
--- a/clang/lib/CodeGen/CGObjCRuntime.h
+++ b/clang/lib/CodeGen/CGObjCRuntime.h
@@ -211,6 +211,11 @@
   /// implementations.
   virtual void GenerateProtocol(const ObjCProtocolDecl *OPD) = 0;
 
+  /// GetOrEmitProtocol - Get the protocol object for the given
+  /// declaration, emitting it if necessary. The return value has type
+  /// ProtocolPtrTy.
+  virtual llvm::Constant *GetOrEmitProtocol(const ObjCProtocolDecl *PD) = 0;
+
   /// Generate a function preamble for a method with the specified
   /// types.